Alexander Aring <alex.aring@xxxxxxxxx> wrote:
> _All_ current supported transceivers have on hardware side _one_
> framebuffer only.
> I would agree 3-4 frames should keep the transmitter buffer, because
> only one framebuffer, 250kBit (even slower on sub 1-GHz) and holding
> 3-4 skb's in background.
If we are counting frames rather than packets, then I agree that 3-4 is too
low; we should accomodate 2-3 full-sized IPv6 packets worth of fragments.
1280 / 88 = 14 * 3 = 42.
So I suggest somewhere between 32 and 48 as a good default.
Well, we really ought to use the BQL to get the right number!
https://lwn.net/Articles/469652/
> On most systems the qdisc default is pfifo (but I remember something
> that systemd changed to fq_codel as default).
yes, fq_codel is often the default now.
> This will getting the queue full and with payload of 352 bytes it makes
> fragments invalid because pfifo will drop some which is part of the
> whole fragment.
I had assumed that the fragmentation happened after the qdisc.
> What I know is, when we drop one fragment, then we could drop every
> fragment inside the queue which comes from the whole fragmented 6lowpan
> packet. it seems this will not be handled currently.
This is very important, and why I had assumed that fragmentation was
afterwards.
--
] Never tell me the odds! | ipv6 mesh networks [
] Michael Richardson, Sandelman Software Works | network architect [
] mcr@xxxxxxxxxxxx http://www.sandelman.ca/ | ruby on rails [
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